The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a plasma reactor necessary to remove material from and deposit material to a substrate. In general, plasma is formed within the plasma reactor under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
During, for example, a deposition or an etch process, monitoring the plasma processing system can be very important when determining the state of a plasma processing system and ensuring the quality of devices being produced. Additional process data can be used to prevent erroneous conclusions regarding the state of the system and the state of the products being produced. For example, the continuous use of a plasma processing system can lead to a gradual degradation of the plasma processing performance and ultimately to complete failure of the system.
Plasma can enable and/or enhance processes used by the semiconductor industry. In many instances it is critical that semiconductor equipment possess a mechanism for determining plasma presence to complete a process. In fact, proceeding with the manufacture of semiconductor devices without a plasma, when one is expected, often results in the scrapping of product.
Many techniques are available to monitor and detect the presence of plasma, however, most require cost prohibitive components and/or require physical contact with the plasma.